Minimally invasive surgery has brought about significant economies in hospital costs and patient productivity largely because of reduced hospital confinement and patient rehabilitation time. The instruments used to perform such surgery however, still contribute substantially to the expense of the surgery because of the miniturization required of such instruments, sterilization requirements, and material costs. Retractor instruments of the prior art for minimally invasive surgery are usually of a spring wire construction or made of a multi-joint lever system composed of a plurality of metallic support arms which are pivotally interconnected to form a truss support platform. The manufacturing and material costs of metallic retractors is substantially more expensive for metallic retractors than plastic retractors and therefore the use of metallic retractors as disposable retractors is economically restrictive. A disposable retractor made of a plastic material molded such that the retractor has a continuous truss surface with self-hinging joints integrally formed with the surfaces presents an instrument which is readily sterilizable and inexpensive to manufacture; non-disposable retractors, on the other hand, to be reusable, require sterilization after each use. Metallic multi-joint lever system-type retractors having support arms pivotally hinged to each other are less readily sterilized because of the tendency of small particles to adhere to pivoting joints. These retractors are prohibitively expensive for disposable use and present increased surgical risk without cost reduction due to the sterilization process required after each use.